The present invention relates to a discharge circuit and a duty ratio setting method.
Conventionally, a multiple-battery power supply method used for a data processing apparatus (or unit) supplies power simultaneously from a plurality of batteries with the same characteristics.
Referring to FIG. 4, a discharge circuit using the conventional Power supply method will be described.
The conventional discharge circuits shown in FIG. 4 comprises a battery 4 and a battery 5, which have the same characteristics, and a data processing apparatus 8 which comprises a DC/DC converter 3, a switching element 9 connected to the DC/DC converter 3, and a unit load 7.
Turning on the switching element of the conventional discharge circuit with the configuration described above causes the battery 4 and the battery 5 to discharge simultaneously, this configuration can decrease the discharge rate of each battery and increase battery efficiency.
However, various problems have been encountered in the art in the course of investigations toward the present invention. That is, if a plurality of batteries, each with its own characteristics, is connected to the conventional discharge circuit described above, the battery with the highest voltage discharges first. Therefore, the discharge ratio between the battery 4 and the battery 5 depends on the voltage characteristics. That is, the battery 4 or the battery 5, whichever is higher in voltage, discharges first. As a result, the problem with the conventional circuit is that the battery with the highest voltage loses its capacity first and, after that, the battery with the lowest voltage is subjected to discharge alone.
Therefore, the conventional discharge circuit does not make the best use of simultaneous discharging, and during discharging, the remaining battery capacity varies among batteries.
The present invention seeks to solve the problems associated with the prior art described above. It is an object of the present invention to provide a discharge circuit and a control method of discharging that allow a plurality of batteries a simultaneous discharging regardless of their battery voltages. Other objects of the present invention will become apparent from the entire disclosure.
According to a first aspect of the present invention, there is provided a discharge circuit comprising at least two batteries, a plurality of switching elements connected to the batteries, and a DC/DC (Direct Current/Direct Current) converter controlling ON/OFF states of the plurality of switching elements, wherein a duty ratio setting unit is connected to the DC/DC converter, the duty ratio setting unit checking capacities of the batteries, calculating a duty ratio based on a battery capacity ratio calculated from the capacities of the batteries to determine a switching timing in which the plurality of switching elements are to be switched, and setting the duty ratio in the DC/DC converter.
The discharge circuit with this configuration sets the duty ratio in the DC/DC converter based on the battery capacity ratio calculated from the capacities of the batteries. Therefore, the batteries are simultaneously discharged regardless of their voltages, and the plurality of batteries may be used up at the same time.
According to a second aspect of the present invention, there is provided a discharge circuit, wherein the duty ratio setting unit checks remaining capacities of the batteries, calculates a new duty ratio based on the battery capacity ratio calculated from the remaining capacities, and updates the duty ratio set in the DC/DC converter.
In accordance with the second aspect, the duty ratio may be changed based on the capacity ratio. Therefore, it is assured that the batteries are simultaneously discharged regardless of their voltages, and the plurality of batteries may be used up at the same time.
According to a third aspect of the present invention, there is provide a duty ratio setting method comprising the steps of: detecting capacities of at least two batteries; calculating a battery capacity ratio from the battery capacities followed by calculating, based on the battery capacity ratio, a duty ratio which determines a switching timing in which a plurality of switching elements connected to the batteries are to be switched; and transmitting the duty ratio to a DC/DC converter as a signal to set the duty ratio in the DC/DC converter.
In accordance with the duty ratio setting method comprising those steps, the duty ratio based on the battery capacity ratio calculated from the capacities of the batteries may be set (and updated) in the DC/DC converter. Therefore, the batteries may be simultaneously discharged regardless of their voltages, and the plurality of batteries may be used up at the same time.
According to fourth aspect of the present invention, the duty ratio setting method further comprises the steps of: checking remaining capacities of the batteries when the battery capacity ratio varies caused by discharge of the batteries; calculating a remaining capacity ratio between the batteries based on the remaining capacities of the batteries to calculate a new duty ratio from the remaining capacity ratio of the batteries; and transmitting the calculated new duty ratio to the DC/DC converter as a signal to change the duty ratio that is set in the DC/DC converter.
In accordance with the duty ratio setting method of the fourth aspect, the new duty ratio based on the remaining capacity ratio calculated from the capacities of the batteries is set in the DC/DC converter to change (update) the old duty ratio. Therefore, the batteries may be simultaneously discharged regardless of their voltages, and the plurality of batteries may be used up at the same time.
According to a fifth aspect, there is provided a computer readable program product which sets a duty ratio, the program causing a processor to check capacities of at least two batteries; calculate a duty ratio which determines a switching timing in which a plurality of switching elements connected to the batteries are to be switched; and send the duty ratio to a DC/DC converter as a signal to set the duty ratio in the DC/DC converter.
The duty ratio setting program comprising those steps sets the duty ratio, which is based on the capacity ratio of the batteries calculated from the capacities of the batteries, in the DC/DC converter. Therefore, the batteries may be simultaneously discharged regardless of their voltages, and the plurality of batteries may be used up at the same time.
The program product is carried by a medium, typically a recording medium, which, however, includes a static/nonstatic or dynamic medium, also including a carrier wave carrying the program via transmission lines or networks.